Printed circuit assemblies (PCAs) typically include components that generate heat during operation. For example, PCAs commonly include heat generating ball grid array (BGA) packages, such as application specific integrated circuits (ASICs). Some components generate a significant amount of heat and active removal of heat is employed to avoid premature failure of the component. Cooling these heat generating components is a challenge for optimal performance and reliability.
Various heat removal techniques are currently being used in PCAs. Many of the techniques effectively remove heat from the PCA. Expensive heat removal techniques, however, are typically employed to adequately remove heat from significant heat generating components. Examples of current heat removal techniques include package heat spreaders, natural convection, heat sinks, forced convection, and conduction through the bottom of a printed circuit board. Heat removal techniques on the top of the component, such as fans and various heat sink types, are common. Sinking heat from the bottom side of a component package is less common.
One bottom side of component heat sinking technique employs a thick and malleable conductive pad sandwiched beneath the PCA and in contact with a conductive substrate. Some disadvantages to this technique are, due to the volume of the material, the cost is high and the heat transfer is not very effective. Additionally, the conductive pad is often a weak point of heat transfer. With conduction through the bottom of the PCA, the conductive substrate is often a significant distance away to accommodate backside components and keep out distances (i.e. the minimum distance that must be maintained between the printed circuit assembly and the adjacent structures in order to avoid electrical shorts or physical impact damage).